We proposed strengthening and toughening mechanisms of nanocomposites based ondislocation activities in brittle ceramics.We took notice that an intra-type nano-structurecould only have the potential to improve strength and fracture toughness due to dislocationsformed around the dispersed particles.In this work,we prepared nickel dispersed aluminacomposites powders with 10 wt%a-alumina as a seeds using a novel soaking method andsintered by pulse electric current sintering (PECS)technique.The maximum strength of thealumina-nickel nanocomposites was 984 Mpa after being sintered at 1450 °C,where thespecimen size was 2×2×10 mm 3 .The maximum fracture toughness was 5.5 Mpa-m 172 afterbeing sintered at 1350 °C measured by a single edge V-notched beam (SEVNB)method.Thespecimen sintered at 1350 °C with seeds was carried out heat-treatment under Ar atmosphere.We changed heat-treatment temperature from 800 °C to 1000 °C and keeping time at thattemperature from 0 min to 10 min.The value of fracture strength after heat-treatment showedsimilar that with before heat-treatment.However,the fracture toughness was remarkablyincreased to 7.6 Mpa·m 172 in annealed specimen at 800 °C for 5 min.This fracture toughnessvalue showed about 2 times larger than that of monolithic alumina.
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